Recherche dans des sols sahariens d’actinobactéries à activité contre Escherichia coli

Abstract

The work aims to isolate, from Saharan soils actinobacteria producing antibiotics against Escherichia coli. For this purpose, we chose two soil samples taken from a palm grove and from a reg in the wilaya of Timimoune. By using a chitin medium, with or without the addition of selective antibiotics, we were able to isolate a large number of actinobacteria. Then, 100 isolates were selected based on morphological criteria, and after their purification, we obtained only 74. The test of this number by the cross-streak method against strains of E. coli on ISP2 medium revealed only 3 isolates with activity against E. coli. These isolates are TR7, TR14 and TP17. Their morphological study showed the probable belonging of TR7 and TR14 to the genus Streptomyces while, TP17 to the genus Streptoverticillium. The results of the production kinetics on liquid medium were negative whereas, these results on solid medium showed maximum activity in the 2nd day of incubation with an inhibition diameter of 28mm for isolate TR14 and 23mm for isolate TR7. The antibiogram test of the methanolic extract of the solid medium revealed an inhibition diameter of 8 mm.